Spring applied emergency brake

ABSTRACT

An emergency brake mechanism for use in the cage of a hoist comprising a pair of brake members spring-biased towards opposed cooperating surfaces on a hoist tower, said brake members being linked through a spring relief means which ensures a gradual application of the brake members.

llnited States Patent Shalders [451 Jan. 18, 1972 SPRING APPLIEDEMERGENCY BRAKE Inventor: Alan John Shalders, Tolworth, EnglandAssignee: A.C.E. Machinery Limited Filed: Nov. 26, 1969 Appl. No.:880,125

Foreign Application Priority Data Dec. 9, 1968 Great Britain ..58,407/68US. Cl ..188/189, 188/44 Int. Cl Fl6d 59/00, B61h 11/02 Field of Search..188/44, 136, 187-189 [56] References Cited UNlTED STATES PATENTS1,165,583 12/1915 Farmer..... ...l88/l89 2,717,663 9/1955 Higgins 188/443,215,231 11/1965 Lodige ..188/189 Primary Examiner Duane A. RegerAttorneyNorris & Bateman [5 7 1 ABSTRACT An emergency brake mechanismfor use in the cage of a hoist comprising a pair of brake membersspring-biased towards opposed cooperating surfaces on a hoist tower,said brake members being linked through a spring relief means whichensures a gradual application of the brake members.

5 Claims, 3 Drawing Figures PATENTEBJAN18 r972 SHEET 1 [1F 2 InventorALAN JOHN SHALDERS PATENTEU JAN18|972 3.635.315

sum 2 OF 2 Inventor ALAN JOHN SHALDERS Attorneys Q. LVN/5,1,0 DOLGMQ/MSP6 APPLIED EMERGENCY BRAKE The invention relates to hoists of the typeused on building sites and is particularly concerned with emergencybrake mechanisms for use in the cages of such hoists.

In the operation of hoists it is highly desirable to have an emergencybrake situated on the hoist cage adjacent a part of the hoist tower toarrest the cage in the event of cable failure or failure in the windingmechanism. The brake normally includes a pair of brake membersspring-biased towards cooperating surfaces carried by or on the towerand held therefrom by a member under the control of an overspeedgovernor linked to a follower roller running against the side of thetower. The brake is normally arranged to be actuated by excessive speedin either direction.

A disadvantage with existing emergency brake mechanisms is that theyoperate with a grab" or snatch" action which brings a cage to an abrupthalt and can cause injury to occupants of the cage by throwing themabout when the emergency brake mechanism operates.

The present invention aims to provide an emergency brake mechanism inwhich the brakes are applied gradually to avoid the abrupt haltof thecage encountered with the existing brake mechanisms.

According to the invention, there is provided an emergency brakemechanism for use in the cage of a hoist comprising a pair of brakemembers spring-biased towards opposed cooperating surfaces on a hoisttower, said brake members being linked through a spring relief means toensure a gradual application of the brake members. The spring reliefmeans preferably takes the form of a number of disc springs or dishedwashers.

The brake members may take the form of wedge-shaped brake shoesarranged, upon actuation, to run up a pair of inclined surfaces and tobe forced into engagement with braking surfaces on a guide rail on thehoist tower. The braking surfaces may be provided on the outer surfacesof the rail or on the inner surfaces of a channel-shaped rail.

The inclined surfaces are preferably mounted on support members whichare independently pivoted on vertical axes and are connected by thespring relief means so that, on initial actuation of the brake the brakemembers run up the inclined surface and force the supports against thespring means which then return to apply the brakes firmly.

In an embodiment of the invention, a hoist tower is built up on two ormore parts from triangular sections connected together by spigot jointsand socket joints. The sections each carry a vertical guide rail,comprising a substantially rectangular welded tube, each guide railsection also being connected by spigot joints.

An emergency brake mechanism according to the invention is mounted on aframe which is secured to a cage for the hoist and the brake mechanismis arranged to be actuated by an overspeed governor controlled by afollower moving along the guide rail.

The invention will now be further described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is an elevation of one embodiment of an emergency brake mechanismaccording to the invention;

FIG. 2 is a section on line lI-II in FIG. 1; and

FIG. 3 is a section on line III-I1I in FIG. 2.

Referring to the drawings, the emergency brake mechanism comprises apair of brakeshoe or like members 1 provided on their facing surfaceswith linings 2. As shown in the drawings, the brakeshoes l are wedgeshaped and are engageable with a pair of correspondingly shaped brakesupport members 3 which are held in brackets 4 as shown in FIG. 2. Thelarger ends of the brakeshoes l are slidably received in a bracket 5 towhich a pair of guide rods 6 are secured. The guide rods 6 pass throughthe brackets 4 and act as pivot pins for said brackets. A rod 7 is alsosecured to the bracket 5 and carries a collar 8 and a coil spring 9. Thecoil spring 9 bears at one end against the collar 8 and at the other endagainst a head member 10 provided at the upper end of rod 7. The headmember 10 is provided with a pivot for one end of a lever 1 l the otherend of which is pivotally connected to a lever 12 which in turn ispivotally connected to a frame 13 for the mechanism. The levers l1 and12 form a toggle linkage which is normally held at its center pivotagainst an adjustable stop 14 mounted on the frame 13 by a lever 15which is pivotally mounted on a pin 16 on the frame. The lever 15 isarranged to be held in the position shown in the drawings by means of acoil spring 17 which urges said lever against an adjustable stop 18. Thelever 15 is also provided with a bore 19 whereby said lever may beconnected to the release lever of an overspeed governor (not shown).

The brackets 4 are provided with lugs 20 which are received in channelmembers 21 on the frame 13. The brackets 4 are connected by means of thelugs 20 by providing each of said lugs with a bore through which a bolt22 is passed to be engaged by a nut 23. Disc springs 24 are provided onthe bolt between the lugs.

The frame 13 of the mechanism is mounted on a cage for a hoist with thebrakeshoes 1 arranged on either side of a guide rail 25 of the hoist asshown in FIG. 2. When the cage is operated normally, the variouscomponent parts of the brake mechanism assume the position illustratedin the accompanying drawings.

In the event of the cage exceeding a predetermined speed, the overspeedgovernor is effective to cause the release lever to release lever 15.The lever 15 is forced by coil spring 17 to pivot about pin 16 and tomove clear of the toggle linkage 11,12. This linkage is forced upwardlyby the spring 9 and the rod 7 and bracket 5 are also forced upwardly.The brakeshoes 1 are entrained by the bracket 5 and act against thebrake support members 3 which are urged away from each other and causethe brackets 4 to pivot about the guide rods 6 and compress the discsprings 24. The disc springs reexert themselves and force the brakesupport members 3 towards each other which in turn act on the brakeshoes1 to force the linings 2 against the guide rail 25 to progressively slowand finally halt the cage. The return action is gradual so that thebrakes do not operate with a snap action but are applied progressivelyand firmly thus preventing the cage from grabbing" or snatching duringemergency braking.

The brake mechanism can be adjusted for any suitable cage and hoist asfollows. The first adjustment is to the stop 18, which may take the formof a bolt passing through a bore in a lug on the frame 13 and secured tothe lug by a pair of locknuts. The stop is so arranged that when thelever 15 is held by the release lever, said lever 15 is substantiallyhorizontal. A disc 26 is preferably provided on the pivot between leversl1 and 12 and one side of the disc bears against the end of lever 15.The stop 14 is adjusted so that there is a clearance of 0.002-0.005 inchbetween the end of the stop and the disc 26. The stop may take the formof a bolt engageable in a screwthreaded bore in the frame 13 andsecurable by means of a locknut. The adjustable stop 14 is provided toensure that the toggle linkage 11,12 cannot pass through the centerposition and thereby render the lever 15 inoperative.

The third adjustment is to the nut 23 and bolt 22 which are tighteneduntil the disc springs 24 are under a predetermined desired tension inthe inoperative position of the brake mechanism. The fourth and finaladjustment is to the spring rod 7 the effective length of which isadjusted to give the coil spring 9 a working length of about 4% inch.This adjustment is preferably achieved by providing the end of the rodremote from head member 10 with a screw thread which is engaged by apair of nuts one on each side of the bracket 5.

lclaim:

1. An emergency brake mechanism for use in the cage of a hoist havingopposed guide surfaces, said brake mechanism being normally retractedand spring-biased toward said guide surfaces, said brake mechanismcomprising a pair of relatively movable brake members linked by springrelief means and having inclined surfaces, a pair of relatively movablewedge- 3. A mechanism as claimed in claim 1, wherein the spring reliefmeans comprise a number of disc springs or dished washers 4. A mechanismas claimed in claim 1, wherein said opposed braking surfaces areprovided on the outer surfaces of the guide rail.

5. A mechanism as claimed in claim 1, wherein the guide rail is channelshaped and said opposed braking surfaces are provided on the innersurfaces of said channel.

It i t i i

1. An emergency brake mechanism for use in the cage of a hoist havingopposed guide surfaces, said brake mechanism being normally retractedand spring-biased toward said guide surfaces, said brake mechanismcomprising a pair of relatively movable brake members linked by springrelief means and having inclined surfaces, a pair of relatively movablewedge-shaped brakeshoes adjacent said guide surfaces, said inclinedsurfaces being arranged, when the brake mechanism is energized to movesaid brakeshoes toward applied position, to be engaged by saidbrakeshoes which are displaced thereby toward said opposed guidesurfaces, said spring relief means providing gradual brake application.2. The brake mechanism defined in claim 1, wherein said brake membersare independently pivoted about spaced parallel axes, and saidbrakeshoes are disposed laterally between said inclined surfaces and atopposite sides of a guide rail providing said guide surfaces.
 3. Amechanism as claimed in claim 1, wherein the spring relief meanscomprise a number of disc springs or dished washers.
 4. A mechanism asclaimed in claim 1, wherein said opposed braking surfaces are providedon the outer surfaces of the guide rail.
 5. A mechanism as claimed inclaim 1, wherein the guide rail is channel shaped and said opposedbraking surfaces are provided on the inner surfaces of said channel.